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Sat in traffic from downtown Dallas to the dyno shop about 26 miles away. Not fun.

When I got there, I got about 5 minutes of cooldown before he drove the car onto the rollers, strapped me down, and did the first 2 pulls. Both were about 2hp-ish below my "best" pulls, including a major dip in torque. The operator then gave me about 10-15 minutes of cooldown. At this point another guy came in to do my last pull. I went to the adjoining room to watch the graph in progress. Although initial torque was down, peak torque and hp were slightly above my last session (as the graph was up as a reference). I was excited, and then he cut it off at 6200 (before my car usually peaks). I think peak torque hit 221 on that pull. I walked into the room as he was about to pull the straps. I let him know what happened and he said he'd do another pull. He got right in the car and started it up (no cooldown). After the pull, he realized that he hadn't started the sampling... lovely. So he immediately started again. Needless to say, numbers were even lower. I felt quite defeated last night.

On a positive note, my son is looking good! His size is actually almost 3 weeks ahead of schedule (I was also a big baby). I'm happy he's big and strong!

You're probably very right about this. I have an opportunity to have some good tuning done, but it involves running a different fuel filter and an AFPR. Not sure if I'm ready to mess with all that, yet. Software would be free for me. He claims he's been making an additional 10-15hp over standard NA tunes.

Quote:

Originally Posted by vI6ious

you need a tune bad,

Little analogy, your car is an Olympic Athlete but its brain is at a high school All-State level.

Or maybe something like your car is a high powered NFL offense, but your quarterback is better than average at the collegiate level.

The y-pipe was already fab'd when I got the exhaust. I just had Stett weld it up into place, mainly. It's about 2 inches coming off the headers, and they merge to 2.5 and it expands to 3. I think it'd be better if they merged into a 3.

The flanges are from the original exhaust and are 2.05 OD. The piping running to the merge is the same, 2.05 (I just measured). Where it merges is 2.39 OD. It expands to the 3 inch in about 6-7 inches.

Quote:

Originally Posted by beemka

if you can post internal diameters of your pipes before and after the merge, I think I can tell why you lost torque.

glad to hear about your son, sad to hear about the crappy pulls. Hopefully you can go back and get one solid cool pull to see where you are really at. BTW did the dive at 4200 dissappear or did it get worse?

Still has a small step, but not nearly as long. The merge into the neck is much smoother, too.

Just need to get some money together. Dang, so many things to do.

By the way, if anyone wants to donate to help with this research, I accept Paypal

I actually had one very nice Fanatic donate to help with this dyno. I won't name him, because I don't think he'd want everyone hitting him up for cash, haha! (But, thank you very much, it is appreciated).

According to my knowledge, after quite extensive reading about exhaust design, I can say that when you merge two pipes into one, the perfect ratio of pipe internal diameter before and after is 1.1892 In your case (don't have ID,so I'll use OD) 2,05 x 1,1892 = 2,4379 <-- that's the diameter of your ideal "aftermerger". I know it may seem small, but you should consider, that the exhaust gases from particular cylinders don't run through the same pipe at the same time. What's more, with a bigger pipe, you loose a lot of gas velocity, especially at low revs, slow flow means also gas temperature drop => fumes become denser. Exhuast gases have an inertia. When they escape the cylinder, behind them creates itself an area of lower pressure which, during valve overlap, pulls the A/F mixture into cylinder. That means better VE and more torque. And that has nothing to do with harmonics, that's a different story. In this case, it's about dynamic work of gases. Now, IMO, because of 3' piping, you have slow flow and dense fumes at low revs. And this situation substantially ruins the "inertia effect" and thus your torque.
BTW, I really don't think the merge design is to be blamed for your duno results.
But, I'm not an expert, and that's just my 0,02c
ps.
sorry for my english - I'm still learning.

No worries about your english. It's better than what I usually see on the forum.

I definitely appreciate your input.

Quote:

Originally Posted by beemka

According to my knowledge, after quite extensive reading about exhaust design, I can say that when you merge two pipes into one, the perfect ratio of pipe internal diameter before and after is 1.1892 In your case (don't have ID,so I'll use OD) 2,05 x 1,1892 = 2,4379 <-- that's the diameter of your ideal "aftermerger". I know it may seem small, but you should consider, that the exhaust gases from particular cylinders don't run through the same pipe at the same time. What's more, with a bigger pipe, you loose a lot of gas velocity, especially at low revs, slow flow means also gas temperature drop => fumes become denser. Exhuast gases have an inertia. When they escape the cylinder, behind them creates itself an area of lower pressure which, during valve overlap, pulls the A/F mixture into cylinder. That means better VE and more torque. And that has nothing to do with harmonics, that's a different story. In this case, it's about dynamic work of gases. Now, IMO, because of 3' piping, you have slow flow and dense fumes at low revs. And this situation substantially ruins the "inertia effect" and thus your torque.
BTW, I really don't think the merge design is to be blamed for your duno results.
But, I'm not an expert, and that's just my 0,02c
ps.
sorry for my english - I'm still learning.

No problem, I'd really like to hear Burns opinion about that. If you look at this sitehttp://www.burnsstainless.com/2into1.aspx
you can't find a 2in1 merge collector, that even predicts such a "hardcore" ratio of diameters as yours. They almost never exceed 1.4 and I'm pretty sure, the HC ratios are for turbocharged engines only, n/a usually run much lower ratios.Oobvioulsy good for turbo application =/= good for N/A engine.